The shape of a dental restoration is typically determined dependent on the shape of at least one tooth that neighbors a tooth or teeth to be restored. Such a neighboring tooth may be an adjacent tooth of the tooth to be restored in the same jaw or an opposite tooth of the tooth to be restored in the opposing jaw. Further at least part of the shape of the tooth to be restored may eventually be used to determine the shape of the restoration if residual structure of that tooth is present.
Further for determining the shape of the dental restoration the possible movements of the upper and lower jaws must typically be accounted for, particularly when the jaws are closed so that at least one tooth of the upper jaw is in contact with a tooth of the lower jaw. Such a situation is typically referred to as the teeth being in “occlusal contact” in dentistry. This is because opposing teeth in a patient's mouth typically frequently contact each other in different positions relative to one another, for example during chewing. Therefore a good fit between the restoration and an opposing tooth or opposing teeth must be ensured not only in one position but rather in various positions of the jaws relative to one another. Further the jaws can typically be moved relative to one another with the teeth remaining in occlusal contact, as it also often occurs for example during chewing. Such a movement of the jaws relative to one another with the teeth being in occlusal contact is typically referred to as “articulation” in dentistry. Therefore for the preparation of a dental restoration the articulation is typically determined and simulated for precisely fitting the dental restoration to one or more opposing teeth.
There are various methods for simulating the articulation, one of which comprises manual articulation by use of a mechanical articulator. Such a mechanical articulator typically reproduces the human upper and lower jaws which are movably connected by a joint. The reproduced jaws are further adapted to receive models of a patient's jaw that also represent the patient's teeth so that the articulation can be simulated. The dental restoration may be placed in a model to test its fit relative to neighboring teeth under simulated articulation. The joint of such an articulator is typically designed to resemble the mechanical interaction of the bones forming the joint. That joint is typically referred to as “temporomandibular joint” in dentistry. The mechanical interaction of bone joints is more complex that a simple mechanical hinge, and in particular may provide for a movement which deviates from an ideally circular movement around a pivot axis as provided by a hinge. Further a bone joint may also allow movements radially and axially from the pivot axis. There are different articulators which resemble the temporomandibular joint at different quality. Articulators that are designed to more precisely resembling the temporomandibular joint are often also more complex in use and more expensive than other articulators having a simpler configuration.
Because the precision of a simulated articulation may be important to provide a precisely fitting dental restoration approaches have been developed which include the use of computers.
For example U.S. Pat. No. 6,431,871 B1 discloses a method which comprises the steps of producing casts of the upper and lower jaw from an impression, coordinating them using an articulator, coordinating reference points on the jaw casts with the rotation axis of the articulator, arranging the jaw casts in a measuring device for determining the geometry of the tooth to be restored and the rotation axis of the articulator by use of the reference points, digitizing the jaw casts, and constructing the denture using CAD, and manufacturing the denture using CAM.
US 2009/0068617 A1 discloses methods for acquiring and utilizing time-based 3D jaw motion images to enhance the computer-aided design of dental restorations. The 3D jaw motion images are used to provide a jaw motion model for driving a motion simulation which is used in a computer-aided design of a dental restoration.
Although existing approaches may provide certain advantages there is still a need for facilitating the preparation of dental restorations which precisely fit and cooperate with other teeth in a patient's mouth. Desirably such dental restorations can be prepared largely outside of a patient's mouth and require minimized or no mechanical finishing in shape after placement in the patient's mouth. Further it is desirable that such dental restorations are relatively inexpensive.